"To be honest, I do not feel that I deserve to be in the company of so many of the transformative figures who've been honored by this prize," Obama said in brief remarks at the White House. "I do not view it as a recognition of my own accomplishments but rather as an affirmation of American leadership on behalf of aspirations held by people in all nations."

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The president said the prize has been used as a means to provide momentum, but that no one person or one administration alone can solve all the problems.

"All nations must take responsibility for the world we seek," the president said. "We cannot tolerate a world in which nuclear weapons spread to more nations. ... We cannot accept the growing threat posed by climate change, which could forever danger the world we pass on to our children. ... We cannot allow the differences between people to allow the way we see one another."

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Emphasizing the work he has done as commander in chief in pulling back forces from Iraq, Obama said that "some of the work confronting us will not be completed during our presidency" and that some work "may not be completed during my lifetime." But he added that he was hopeful the challenges will be met.

"This award is not simply about the efforts of my administration, it's about the courageous efforts of people around the world," he said.

Obama, only the third sitting U.S. president to win the prestigious award, will travel to Oslo in December to accept the prize in person. The White House says Obama will donate the full balance of the prize -- $1.4 million -- to charity but they did not say which charity, or charities, he has chosen.

The news that Obama was awarded the 2009 Nobel Peace Prize came as a surprise even to the White House. Press aides said they had heard from news reports weeks ago that the president had been nominated for a Nobel Peace Prize, but they do not believe Obama himself knew of his nomination.

The deadline for nominations is Feb. 1, meaning the president was nominated after being in office for just 11 days.

The award is "extraordinarily unprecedented," Michael Worek, author of "Nobel: A Century of Prize Winners," told ABC News.

"It would be like awarding the Oscar halfway through the movie. You're not saying it's a bad movie, you aren't knocking it. But we just don't know how it ends," Worek said.

"President Obama has changed very dramatically international politics," Lundestad told "GMA's" Diane Sawyer today. "We feel he has emphasized multilateral diplomacy, he has addressed international institutions, dialogue negotiations. He has inspired the world with his vision of a world without nuclear arms. He has changed the U.S. policy dramatically. There's a whole list."